The present invention relates to compaction methods and compaction apparatus and in particular but not exclusively to methods and apparatus for compacting (i.e. compressing) waste material. Other applications for the invention include the compaction of waste materials used in farming and the food industry, but not necessarily waste materials.
Compacting apparatus is described in International Patent Application No. WO 94/07688. That apparatus uses a hopper to supply material to a screw conveyor which conveys material through a passage to cause compaction. The compacted material then leaves through an exit nozzle. A control circuit is provided to sense when the compacting apparatus becomes blocked. When this happens, the screw conveyor is reversed to draw compacted material back to the hopper, with a view to clearing the blockage. It has been found that even if this technique for clearing blockages is effective, its reliance on a potentially complex and expensive control arrangement can prevent its use for certain commercial applications, particularly with relatively small, cheap compacting apparatus. The present inventor has therefore sought to provide improved compacting apparatus.
The present invention provides compacting apparatus comprising a screw conveyor for axial rotation to convey material through a passage and compact it therein, and an exit nozzle communicating with the passage, the screw conveyor being supported for axial movement relative to the passage during use, whereby the screw conveyor may move axially in the event of a blockage.
The screw conveyor is preferably resiliently biased in the axial direction relative to the passage. The screw conveyor may be biased to move relative to the passage in the conveying direction. At least part of the screw conveyor is preferably located within a tapering part of the passage and has a diameter which tapers in the same sense, whereby axial movement of the screw conveyor relative to the passage varies the gap between the tapering part of the screw and the tapering part of the passage. The tapering parts of the screw conveyor and passage may have substantially the same degree of taper.
Preferably fixed blade means are located adjacent the screw conveyor, and cooperating blade means are carried by the screw conveyor, whereby material located between the said blade means is subjected to a cutting action by continued rotation of the screw conveyor. The cooperating blade means may be located along the outer edge of the flight of the screw conveyor. The cooperating blade means may extend over a greater axial length of the screw conveyor than the fixed blade means, whereby the blade means remain in cooperation over a range of positions of the screw conveyor relative to the passage. Preferably at least part of the cooperating blade means are located along a tapering portion of the screw conveyor.
In a second aspect, the invention provides compacting apparatus comprising a screw conveyor for conveying waste material through a passage and compacting it therein, and an exit nozzle communicating with the passage, the nozzle defining an internal transverse cross-sectional area which enlarges and reduces respectively in response to increasing and decreasing material pressure, and wherein the nozzle comprises at least one resilient member which causes the nozzle to be biased toward a position of minimum cross-sectional area, the or at least one resilient member comprising an inflatable portion which provides an adjustable degree of resilience dependent upon the degree of inflation of the resilient portion.
Preferably the nozzle has a plurality of wall portions which are movable relative to each other to vary the cross-sectional area of the nozzle, the resilient member cooperating with the wall portions to bias the nozzle toward a position of minimum cross-sectional area.
The nozzle may comprise a number of spaced apart, longitudinally extending fingers. Preferably there are no gaps between the fingers and the nozzle tapers towards its outlet when the nozzle cross-sectional area is at its minimum. The nozzle may comprise two members each of which has a number of spaced apart, longitudinally extending fingers, one member being arranged inside the other. The resilient member may be located to surround the outer of the two members to provide resilient bias thereto. Preferably the two members are arranged such that a finger of one member overlaps two fingers of the other member whereby there are substantially no gaps between the fingers.
In another aspect, the invention provides material handling apparatus comprising compacting means operable to compact material and to deliver compacted material to collection means, the collection means providing a plurality of locations at which compacted material may be received, and being movable to allow one location to move to an emptying position while another is moving to a position for receiving material from the compacting means.
The collection means may comprise a rotatable carousel. Each location may be adapted to removably receive a receptacle which can be removed when full for replacement by an empty receptacle. The receptacle may be a bag or bin liner.
Preferably the apparatus comprises means operable to detect the weight of material received at a location and to cause the collection means to move when the received weight exceeds a threshold value.
Preferably the compacting means comprises a screw conveyor which has a substantially vertical orientation to drive compacted material up to a position from which the material may fall to the collection means.